1. Field of the Invention
The present invention relates to a radar device, and more particularly, to an in-vehicle radar device.
2. Description of the Related Art
As a conventional radar device of this type, there is an in-vehicle automatic cruising device having radar means for detecting an inter-vehicle distance from a preceding vehicle, velocity detecting means for detecting a velocity of a subject vehicle, and arithmetic processing means for outputting a velocity command to a vehicle velocity changing mechanism so as to keep an appropriate inter-vehicle distance on the basis of the inter-vehicle distance and the subject vehicle velocity. The in-vehicle automatic cruising device also includes determining means for determining whether the subject vehicle is in a substantially stop state or a normal travel state on the basis of the inter-vehicle distance and the subject vehicle velocity, and control means for controlling an output of the radar means according to the travel state determined by the determining means. With the above configuration, when the subject vehicle is in the substantially stop state, a power of a laser beam is reduced so that even when an eye of a pedestrian around the subject vehicle is erroneously irradiated with the laser beam, the eye is not injured, thus making it possible to ensure safety of the pedestrian around the subject vehicle (for example, see JP 62-259111 A).
Also, in an energy projection type sensing system in which an energy is projected to the outside to observe a reaction on the basis of the projected energy, there are provided diagnosing means for diagnosing a presence or absence of a state where an adverse affect may occur due to the projection of the energy, energy projection control means for limiting the irradiation of the energy when the diagnosing means diagnoses that the state described above is present. With the above configuration, the system can flexibly cope with a status change of environments to which the energy is to be projected, so as to prevent the subject environment from being adversely affected by the energy projection in advance (for example, see JP 10-2952 A).
At present, a frequency of 76 to 77 GHz of a millimeter wave band is allowed in respective countries for the in-vehicle radar device. For example, in U.S.A., Federal Communications Commission (FCC) regulates transmission outputs of electromagnetic waves at a time of stop and traveling with the in-vehicle radar millimeter wave band, and an upper limit of the transmission output at the time of stop must be smaller than the upper limit of the transmission output at the time of traveling. Hence, in the in-vehicle radar device having a configuration that complies with the FCC, in a case where the transmission output at the time of traveling is larger than the upper limit of the transmission output at the time of stop, the radar device is required to have a function of reducing the transmission output at the time of stop to be lower than the upper limit of the transmission output at the time of stop, or stopping the transmission output in a case where it is unnecessary to detect a target object at the time of stop.
As described above, as the radar device of this type, there is required a radar device that surely stops or reduces the transmission output at the time of stop.